This application claims the benefit of German patent application 10135548.3, filed Jul. 20, 2001, herein incorporated by reference.
The present invention relates generally to open-end spinning devices and, more particularly, to a sliver opening device for an open-end spinning device which comprises a feed device for a rapidly running opening cylinder for opening continuously supplied sliver material.
In addition to the rotor spinning method, a sliver is opened by an opening cylinder into individual fibers in other open-end spinning methods such as friction spinning or air spinning. It is customarily desired in such spinning methods in order to avoid fiber compressions that the sliver material be constantly accelerated over its entire path from the feed device of the opening cylinder to the yarn withdrawal device without the draw-off speed having to assume values that are too high. However, lowering the speed of the opening cylinder as desired for this purpose can be associated with significant disadvantages. There is the danger when the speed of the opening cylinder is lowered that the opening function is adversely affected to a significant extent. The number of interventions of opening elements such as needles or sawteeth into the sliver tuft that are necessary for the desired opening of the sliver material into individual fibers can not be achieved. Both the amount of the combed-out fibers as well as the invariability of this amount is insufficient for an unobjectionable yarn.
German Patent Publication DE 40 40 102 A1 shows a device for spinning a yarn in which device the sliver end is moved into the fittings by an additional airflow so that an effective opening should be possible even if the speed of the opening cylinder is significantly reduced relative to the speed of opening cylinders customary in rotor spinning devices. Because the sliver end is pressed into the fittings, the combing out of fibers, which is substantially brought about by the side flanks of the teeth or needles, is intensified. The attempt is made in this manner to generate a sufficient frictional entrainment even in the case of rather slower combing speeds, which entrainment reliably draws the fibers out of the sliver end or tuft. However, it turned out that as a result of the aspirated drawing in of the individual fibers, the latter are transported with the circumferential speed of the opening cylinder so that, in spite of the reduced circumferential speed of the opening cylinder, the individual fibers have on the whole the same speed as in the case of traditional opening cylinders and are thus undesirably rapid.
German Patent Publication DE 196 10 960 A1 also describes an open-end spinning method in which the individual fibers should no longer be slowed down on their way from the sliver to the yarn. The individual fibers should be subjected immediately after they have been loosened out of the sliver to a precisely determined, mechanically controlled speed. The feed device comprises a very wide feed cylinder and an opening cylinder that is just as wide. This method allows the number of interventions of opening elements into the sliver tuft to be increased.
Presenting multiple slivers, e.g., five slivers, adjacent to each other at the same time is disclosed as a possibility for achieving a wide presentation of fibers. The feeding of several slivers to a spinning location results in significant expense. For example, in addition to the expense occasioned by a multiplication of the feed paths with the required feed elements, the space for a corresponding number of spinning cans at each spinning location must be available. This results in an enormous space requirement for a spinning machine with its plurality of spinning locations. Moreover, very high drafts result between the sliver feed and the spun yarn that endanger the uniformity and the maintenance of the yarn fineness.
It is accordingly an object of the present invention to improve the feed presentation of sliver to the opening device in an open-end spinning device.
The present invention addresses this objective in an open-end spinning device basically comprising an opening device for opening continuously supplied sliver material, the opening device having a feed device for a rapidly running opening cylinder. According to the present invention, a sliver spreading device with at least one cooperating pair of spreading cylinders is arranged in front of the opening device in the feeding direction of the sliver material. The spreading cylinders have circumferential recesses between adjacent circumferential flanges and are arranged in parallel to one another with the flanges of each spreading cylinder engaging into the recesses of the opposing spreading cylinder, whereby the sliver material guided between the pair of spreading cylinders is spread in the axial direction in a cohesive manner over multiple recesses of the spreading cylinders.
In this manner, a sliver can be distributed uniformly over the entire working width of the opening cylinder by the spreading cylinders of the present invention arranged in front of the opening device. A relatively thin feed of fiber material can thereby be achieved. The sliver spreading device advantageously requires little space in comparison to multi-step drafting devices.
A feed of sliver material can be produced with the present invention which feed can achieve a more precise dosing and an elevated uniformity of the fed amount of sliver. The opening process itself is improved. Undesirably high drafts in the direction of sliver flow and the disadvantages associated with them can be avoided.
A compact device for the effective spreading of the sliver in the transversal direction in a narrow space is provided with the sliver spreading device of the present invention. A thin feed of sliver material for the opening cylinder can be achieved that extends over the entire working width of the opening cylinder. This makes it possible to achieve an unobjectionable opening process with a low speed of the opening cylinder and with an opening cylinder that is widened in comparison to the opening cylinder that is customary in rotor spinning. This unobjectionable opening process is distinguished by a high dosing exactitude and high yarn uniformity.
The spacing between the particular cooperating spreading cylinders can preferably be periodically varied. This allows the tensile stress acting on the feed of sliver material to be periodically varied and the spreading process to be intensified, accelerated and evened out in this manner.
In a preferred embodiment, two successive pairs of spreading cylinders are coupled to one another in such a manner that their spreading cylinder spacings vary in opposite directions, i.e., such that the spacing between one pair of spreading cylinders decreases as the spacing between the other pair of spreading cylinders increases. Preferably, the two spreading cylinder pairs are mechanically coupled and a common drive for producing the periodic variation of the cylinder interval is present, whereby the drive for the periodic varying of the spacings is particularly simple and economical and the spreading effect is reinforced even more. In this manner, a sliver can be spread, e.g., to two to three times the original sliver width.
The frequency of the periodic variation of the spreading cylinder spacings is preferably substantially higher than the rotational frequency of the spreading cylinders, e.g., the frequency may be preferably adjusted to a value between 8 Hz and 25 Hz, whereby a high uniformity of the spreading of the sliver material feed results.
The recesses can be designed as trapezoidal grooves. Such a form can be produced in a simple manner and forms deflection edges for the sliver guided in a zigzag manner between the particular cooperating spreading cylinders. The sliver is loaded between the deflection edges with an increasing tensile stress and is effectively spread under the action of this tensile stress.
Alternatively, the recesses and flanges are designed in such a manner that the flanges of the spreading cylinders form an approximate sinusoidal shape in the axial direction. A more protective spreading is achieved in this manner.
In an alternative embodiment of the invention, the spreading cylinders are formed by discs that are fastened to a shaft and whose circumferential surfaces form the flanges. This design can be produced in a simple and economical manner.
A limitation to a maximum of two slivers has the result that the sliver material feed will be stretched primarily by transverse spreading and not primarily by longitudinal draft to a thin fiber fleece when it is fed to the opening cylinder. This can improve the uniformity of the sliver material feed.
A deflection device in front of the sliver spreading device may be arranged at such a spacing for the sliver drawn out of a can that the sliver travels vertically between the can and the deflection device more than the length of one coil of the sliver in the can. This arrangement makes it possible that a false twist introduced into the sliver by the coiler rotation can turn itself out. Such false twists consist of so-called S twists and of so-called Z twists that can be randomly produced when the sliver is deposited. Thus, the deflection device associated with the sliver spreading device reliably avoids such false twists from running into the spreading cylinder pairs and hindering the spreading process.
Further details, features and advantages of the present invention are explained in the following description of a preferred embodiment with reference to the accompanying drawing figures.